Aggregation of 20 nm NPs, IgG, and Tween 20
We had previously tested different surfactants to see if we could get 20 nm polystyrene beads and IgG to stay in suspension while filtering with the centrifuge. We found 0.1% Tween 20 to be sufficient when dealing with 10:1 (5×10^14) 20 nm NPs and 1mg/ml IgG.
During the reverse centrifuge studies we mixed 10^15 particles/ml and 1 mg/ml in 1xPBS and 0.1% Tween 20. After sitting overnight in the fridge we found a settled mass at the bottom of the centrifuge tube. I mixed up a fresh batch and got the same results. I added a lot of additional Tween 20 to see if that would re-suspend the mixture. While it seemed to reduce the amount of settled mass at the bottom, it was still present.
Next I reduced the NP concentration to 10^14 particles/ml. There was very minimal precipitate after spinning at 5 krpm for 5 minutes.
Here are the results from DLS measurements:
